Construction Of Supramolecular Polymers Research Articles

Urea-Functionalized Heterocycles: Structure, Hydrogen Bonding and Applications

Ureido-heterocycles exhibiting different triple- and quadruple H-bonding patterns are useful building blocks in the construction of supramolecular polymers, self-healing materials, stimuli-responsive devices, catalysts and sensors. The heterocyclic group may provide hydrogen bond donor/acceptor sites to supplement those in the urea core, and they can also bind metals and can be modified by pH, redox reactions or irradiation. In the present review, the main structural features of these derivatives are discussed, including the effect of tautomerization and conformational isomerism on self-assembly and complex formation. Some examples of their use as building blocks in different molecular architectures and supramolecular polymers, with special emphasis on biomedical applications, are presented. The role of the heterocyclic functionality in catalytic and sensory applications is also outlined.

Construction of Supramolecular Polymers with Different Topologies by Orthogonal Self-Assembly of Cryptand-Paraquat Recognition and Metal Coordination.

Recently, metal-coordinated orthogonal self-assembly has been used as a feasible and efficient method in the construction of polymeric materials, which can also provide supramolecular self-assembly complexes with different topologies. Herein, a cryptand with a rigid pyridyl group on the third arm derived from BMP32C10 was synthesized. Through coordination-driven self-assembly with a bidentate organoplatinum(II) acceptor or tetradentate Pd(BF4)2•4CH3CN, a di-cryptand complex and tetra-cryptand complex were prepared, respectively. Subsequently, through the addition of a di-paraquat guest, linear and cross-linked supramolecular polymers were constructed through orthogonal self-assembly, respectively. By comparing their proton nuclear magnetic resonance (1H NMR) and diffusion-ordered spectroscopy (DOSY) spectra, it was found that the degrees of polymerization were dependent not only on the concentrations of the monomers but also on the topologies of the supramolecular polymers.

The Solvent Effect on Weak Interactions in Supramolecular Polymers: Differences between Small Molecular Probes and Supramolecular Polymers.

In this minireview, weak interactions that occur in supramolecular polymers are discussed. Combination of weak and strong interactions plays an important role in the construction of supramolecular polymers. It is beneficial to separate the contributions of the weak interactions, as well as each solvent effect on the weak interactions. However, it is generally difficult to observe each solvent effect separately at work in each interaction. Small molecular probes are useful to estimate the contributions of the weak interaction. But, the results should be treated with caution when applied to supramolecular polymer systems. To overcome the problems, a new solvent parameter, solvation ability (SA), is introduced, which was determined on the balance point of extended and stacked forms of porphyrin-based interconvertible supramolecular polymers.

The Effect of Proton Transfer on Redox-Responsive Dimerization in Electroactive 4 H-Bond Arrays

The design of stimuli-responsive systems is an important topic in supramolecular chemistry. These are systems in which an external signal, such as a change in light, temperature, pH or voltage on an electrode, results in structural changes in the supramolecular assembly. Applications include self-healing polymers and gels, controlled release of entrapped molecules and smart materials. Over the years our group has investigated a number of simple systems in which electron transfer is used to perturb the strength of H-bonding interactions. More recently we have expanded the research to include larger H-bond arrays. In particular we have been investigating several different electroactive ureidopyrimidones or UPy’s, which are capable of strong self-dimerization through the formation of 4 linear H-bonds. Non-electroactive UPy’s have already been widely used in the construction of supramolecular polymers and gels capable of self-repair; introduction of electroactive UPy’s in which dimerization can be controlled electrochemically will make even more types of applications possible. These systems are also of interest from a fundamental standpoint in that they provide a well-understood platform in which to investigate the role of intermolecular H-bonding (and proton transfer) on electron transfer.The principle behind redox-responsive H-bonding is straightforward: an oxidation that decreases the negative charge on a H-acceptor (A) or reduction that decreases the positive charge on a H-donor (D) will weaken a H-bond. Alternatively, reduction that increases the negative charge on a H-acceptor or oxidation that increases the positive charge on a H-donor will increase the strength of a H-bond. However, in the latter case, it is possible that oxidation or reduction could also lead to full proton transfer. If this occurs across the H-bond, the primary H-bonds will stay the same, but the secondary H-bonds will change, possibly in a way that has an undesired effect. It is also possible that proton transfer occurs between non-H-bonded sites. This can lead to a H-bonding pattern that is no longer self-complementary. An example of this is found with a UPy we have made that contains a pyridinium redox couple attached to the pyrimidine ring in the UPy, UPyH(MeP+). This UPy was expected and confirmed by NMR to exhibit relatively weak dimerization in CH2Cl2 in the oxidized state due to the electrostatic repulsion and a weaker DADA H-bond motif. Dimerization strength was expected to increase upon reduction to the uncharged radical due to the loss of electrostatic repulsion and increased basicity of the H-acceptor sites. However, the voltammetry observed in CH2Cl2 is not consistent with this result. Furthermore, very similar voltammetry is observed in CH3CN, even though NMR shows only the monomer is present at the same concentrations in this solvent. Studies with model compounds strongly suggest that the reason for the failure to dimerize upon reduction is that the initial reduction product, an uncharged radical, is basic enough to be protonated by the oxidized starting material, resulting in a H-bonding motif that is no longer self-complementary. While this result negates the original goal of strengthening dimerization through reduction, it also opens up the intriguing possibility of switching binding partners by including a guest molecule that is not complementary to the oxidized UPyH(MeP+) form, but is complementary to the reduced, protonated UPyH2(MeP)+ form.

Fluorescent Linear Supramolecular Polymer Based on Host‐Guest Interactions

Construction of supramolecular polymers, in which functional monomer components are held together by noncovalent interactions, is considered as a promising design principle for functional materials. Linear fluorescent supramolecular polymer assembled on account of electrostatic attractions based host‐guest interaction is synthesized and illustrated here. 1H NMR was involved to ensure the structure of guest and polymer, UV–vis and fluorescent spectra were recorded to be a readout signal to investigate the assemble process of polymer. TEM and AFM measurements were carried out to confirm the homogeneous nanometer‐sized molecular assembly. It shows the way to be used as remote readout fluorescent functional material in the future.

Pillararene-Based Aggregation-Induced-Emission-Active Supramolecular System for Simultaneous Detection and Removal of Mercury(II) in Water.

Supramolecular polymers are polymers based on monomeric units held together with directional and reversible noncovalent interactions. Compared with traditional polymers, they possess better processability and better recycling properties, owing to their reversible monomer-to-polymer transition. Herein, we report the construction of a new supramolecular system through self-assembly of a thymine-substituted copillar[5]arene 1 and a tetraphenylethylene (TPE) derivative 2 in the presence of Hg2+. Copillar[5]arene 1 can coordinate with Hg2+ tightly through T-Hg2+-T pairings. On the other hand, 1 can bind with guest molecule 2 through host-guest interactions between the pillararene cavity and the nitrile moiety of 2. These joint interactions generate crisscrossed networks composed of 1, 2, and Hg2+, which eventually wrap into spherical nanoparticles. Due to the aggregation-induced emission (AIE) properties of 2, the formed supramolecular polymer exhibits strong fluorescence which renders convenient the detection of the Hg2+-containing nanoparticles and the subsequent removal procedure. Furthermore, the polymer precipitate can be readily isolated by simple treatment, and the pseudorotaxane 2 ⊂ 1 can be recycled and reused. Our study has demonstrated a practical strategy for the sensing and removal of heavy metal ions in water by the construction of supramolecular polymers.

Construction of supramolecular polymer by enzyme-triggered covalent condensation of CB[8]-FGG-based supramonomer.

A rapid and effective enzymatic strategy for the fabrication of a supramolecular polymer is presented for the first time, in which a bifunctional ternary host-guest supramonomer is first prepared followed by subsequent enzymatic coupling of supramonomers.

The construction of supramolecular polymers through anion bridging: from frustrated hydrogen-bonding networks to well-ordered linear arrays

The construction of supramolecular polymers has been realized by converting random hydrogen-bonding networks into well-ordered linear hydrogen-bonding arrays through an anion-bridging strategy.

ChemInform Abstract: Dynamic Self‐assembly of Coordination Polymers in Aqueous Solution

AbstractReview: 96 refs.

Dynamic self-assembly of coordination polymers in aqueous solution.

The construction of supramolecular polymers has been intensively pursued because the nanostructures formed through weak non-covalent interactions can be triggered by external stimuli leading to smart materials and sensors. Self-assemblies of coordination polymers consisting of metal ions and organic ligands in aqueous solution also provide particular contributions in this area. The main motivation for developing those coordination polymers originates from the value-added combination between metal ions and ligands. This review highlights the recent progress of the dynamic self-assembly of coordination polymers that result from the sophisticated molecular design, towards fabricating stimuli-responsive systems and bio-related materials. Dynamic structural changes and switchable physical properties triggered by various stimuli are summarized. Finally, the outlook for aqueous nanostructures originated from the dynamic self-assembly of coordination polymers is also presented.

テトラキスカリックス[5]アレーンとフラーレンのホスト－ゲスト相互作用による超分子ポリマーの構築

テトラキスカリックス[5]アレーンとフラーレンのホスト－ゲスト相互作用による超分子ポリマーの構築

超分子ポリマーの構築と機能

Recently, much attention has been focused on construction of supramolecular polymers because of their unique structures and functions. Supramolecular polymers are ubiquitous in nature, especially in biological systems, such as microtubules, flagella, virus, and phages. They have unique structures and functions such as self-replication, self-restoration, transportation, and movements. If such supramolecular systems are available by synthetic methods, we are able to obtain various interesting materials and functional devices. In the first part of this review, construction of nano-structures using cyclodextrins as a cyclic building block is described. Rotaxanes and polyrotaxanes of various kinds are introduced. In the last part, construction of supramolecular structures using biopolymers such as DNA and immunoglobulins are described. In this review, I would like to show some recent advances in this field from the viewpoint of polymer science and synthetic chemistry.